Examples of a magnetic material that has high saturation magnetic flux density and a low coercive force and is used for various transformers, various reactors, noise-suppression measures, laser power supplies, pulsed-power magnetic parts for accelerators, various motors, various generators and so on include a silicon steel, ferrite, an amorphous alloy, and an Fe-based nanocrystalline alloy material.
A silicon steel sheet is a cheap material with a high magnetic flux density, but it has a problem in that the magnetic core loss is large for the use in high frequency. From the viewpoint of a producing method, it is very difficult to produce a thin silicon steel sheet equivalent to amorphous ribbons, and, since an eddy current loss is large, a core loss is disadvantageously large. Furthermore, a problem of a ferrite material is that the saturation magnetic flux density is low and temperature characteristics are poor; accordingly, ferrite that readily magnetically saturates is disadvantageous for a high power application where an operating magnetic flux density is large.
A Co-based amorphous alloy has a problem that a low saturation magnetic flux density is 1 T or less for a practical material and thermal stability is poor. Accordingly, when the Co-based amorphous alloy is used in high power use, there is a problem that a part becomes larger and a magnetic core loss increases with time.
Still furthermore, an Fe-based amorphous soft magnetic alloy such as disclosed in PATENT DOCUMENT 1 has excellent squareness characteristics and a low coercive force and exhibits excellent soft magnetic characteristics. However, an Fe-based amorphous alloy system has a physical upper limit value of saturation magnetic flux density at substantially 1.7 T. Furthermore, a problem of an Fe-based amorphous alloy is that magnetostriction is large and the characteristics deteriorate by stress, and another problem thereof is that in an application where currents in the audible frequency range are superposed, sound noise is large. In this connection, a nanocrystalline soft magnetic material such as described in PATENT DOCUMENT 2 has been developed and used in various applications. As an amorphous alloy having higher saturation magnetic flux density, an FeCo amorphous alloy is known. However, a problem of such an amorphous alloy is that the limit value of saturation magnetic flux density is substantially 1.8 T and magnetostriction is very large. As a soft magnetic formed body having high magnetic permeability and high saturation magnetic flux density, a technology such as described in PATENT DOCUMENT 3 is disclosed. Furthermore, in a nanocrystalline soft magnetic material, an attempt has been made to add Co to further improve the saturation magnetic flux density. In PATENT DOCUMENT 4, it is reported that in an FeCoCuNbSiB alloy high saturation magnetic flux density exceeding 1.8 T is obtained.
PATENT DOCUMENT 1: JP-A-05-140703 (paragraph Nos. 0006 to 0010)
PATENT DOCUMENT 2: JP-A-01-156451 (from line 19 in the upper right column to line 6 in the lower right column on page 2)
PATENT DOCUMENT 3: JP-A-2006-40906 (paragraph Nos. 0040 to 0041)
PATENT DOCUMENT 4: JP-A-2006-241569 (paragraph Nos. 0016 to 0017)